The prevalence and clinical presentation of fibularis myofascial trigger points in the assessment and treatment of inversion ankle sprains

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Ankle sprains account for 85% of all injuries to the ankle (Garrick, 1997). Inversion sprains result from a twisting of a weight-bearing foot into a plantarflexed and inverted position leading to lateral ankle ligament injury.
Louwerens and Snijders (1999) state that there are multiple factors involved in ankle sprains or lateral ankle instability. These include injury to the lateral ankle ligaments, proprioceptive dysfunction and decrease of central motor control. Other factors that still need further research include the role of the fibularis muscles, the influence of foot geometry and the role of subtalar instability in ankle sprains (Louwerens and Snijders, 1999). This study focused on the fibularis muscles.
Fibularis longus and brevis muscles are found in the lateral compartment of the leg and function to evert/pronate the foot and plantarflex the ankle. Fibularis tertius is found in the anterior compartment and its function is to evert and dorsiflex the foot. Myofascial trigger points in these three muscles refer pain primarily over the lateral malleolus of the ankle, above, behind and below it (Travell and Simons, 1993 2: 371). This is the exact area where ankle sprain patients experience pain.
Travel and Simons (1993 2:110) state that a once off traumatic occurrence can activate myofascial trigger points. When considering the mechanism of injury of a lateral ankle sprain, the importance of the fibularis muscles becomes obvious. When the ankle inverts during a lateral ankle sprain, these muscles are forcefully stretched whilst trying to contract to bring about their normal action. Therefore these muscles are often injured from traction when the foot inverts (Karageanes, 2004). It stands to reason that as a result of this mechanism of injury myofascial trigger points may develop in the fibularis muscles.
It was hypothesised that fibularis muscle trigger points would prove to be more prevalent in the injured leg when compared to the uninjured leg. To further investigate this hypothesis, an analytical, cross sectional study (phase 1) was done on 44 participants between the ages of 15 and 50. Consecutive convenience sampling was used and participants were screened according to phase 1’s inclusion and exclusion criteria.
According to Travel et al. (1999 1: 19) myofascial trigger points (whether active or latent) can cause significant motor dysfunction. Trevino, et al. (1994) stated that fibularis muscle weakness is thought to be a source of symptoms after an inversion sprain.
Treatment for ankle sprains involves minimising swelling and bruising and encouraging adequate ankle protection in the acute phase. The patient is advised to rest for up to 72 hours to allow the ligaments to heal (Ivins, 2006). After the acute phase has passed, rehabilitation is focused on. This includes improving the ankle range of motion and proprioception. Attention is also given to strengthen the muscles, ligaments and tendons around the ankle joint. In the recommended treatment protocol however, no mention is made of evaluating the musculature around the ankle joint for myofascial trigger points and or treating these points. McGrew and Schenck (2003) noted that if the musculature and neural structures surrounding the ankle joint were affected during an ankle sprain injury, and were left unresolved, they would lead to chronic instability.
It was hypothesised that lateral ankle pain due to inversion ankle sprain injuries may be due to referred pain from the fibularis muscle trigger points.
Patients treated with dry needling of the fibularis muscle trigger points would therefore show a greater improvement in terms of subjective and objective clinical findings when compared to a placebo treatment (detuned ultrasound) applied to the fibularis muscle trigger points.